A key challenge in the wire and cable (W&C) flame resistant sheathing market is to provide a flame retardant composition for flexible wiring use in low voltage personnel electronic applications, including consumer electronics such as cell phone charger wire and computer data, power and accessory cords. Although current insulation materials may provide a balance of mechanical properties and flexibility, the retention on elongation after high temperature heat aging is poor and the wet electrical resistance is low.
Compositions fabricated using a single polymeric system such as polyolefins or thermoplastic elastomers (TPE) such as thermoplastic urethanes lack the necessary specifications to meet all necessary requirements for the flame retardant (FR) insulation market. Thermoplastic polyurethane (TPU)-based, halogen-free flame retardant (HFFR) compositions are typically used for wire insulation/cable jackets for personal electronics to replace halogen-containing polymeric materials. Cable sheathing formed from TPU-based flame retardant (FR) polymer compositions generally fulfill heat deformation testing (UL-1581) requirements at 150° C. that are important in certain W&C applications and which, generally, cannot be achieved with sheathing formed from un-crosslinked polyolefin as a matrix polymer. However, major disadvantages of TPU-based FR compositions is insulation resistance (IR) failure, poor smoke density, high material density, and the high cost of TPU as a raw material.
Using polyolefins to replace TPU could potentially solve problems of TPU-based FR compositions. However, polyolefins or polyolefin elastomer-based HFFR compositions typically suffer from a dramatic drop of heat deformation properties due to a lower melting temperature compared to TPU-based FR compositions, particularly at high temperatures, e.g., 150° C. In addition, the use of polyolefin components typically decrease overall FR performance due to the carbon-hydrogen structure. Consequently, it is difficult for polyolefin-based HFFR compositions to afford a high level of flame retardancy with balanced mechanical properties.